Method for forming fin field effect transistor (finfet) device structure

ABSTRACT

A method for forming a FinFET device structure is provided. The method includes forming a first fin structure and a second fin structure over a substrate and forming a liner layer over the first fin structure and the second fin structure. The method also includes forming an isolation layer over the liner layer and removing a portion of the liner layer and a portion of the isolation layer, such that the liner layer includes a first liner layer on an outer sidewall surface of the first fin structure and a second liner layer on an inner sidewall surface of the first fin structure, and a top surface of the second liner layer is higher than a top surface of the first liner layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of U.S. patent applicationSer. No. 15/669,013, filed on Aug. 4, 2017, the entirety of which isincorporated by reference herein.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are typically fabricated bysequentially depositing insulating or dielectric layers, conductivelayers, and semiconductive layers of material over a semiconductorsubstrate, and patterning the various material layers using lithographyto form circuit components and elements thereon. Many integratedcircuits are typically manufactured on a single semiconductor wafer, andindividual dies on the wafer are singulated by sawing between theintegrated circuits along a scribe line. The individual dies aretypically packaged separately, in multi-chip modules, for example, or inother types of packaging.

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, challenges from both fabrication and design issues haveresulted in the development of three-dimensional designs, such as thefin field effect transistor (FinFET). FinFETs are fabricated with a thinvertical “fin” (or fin structure) extending from a substrate. Thechannel of the FinFET is formed in this vertical fin. A gate is providedover the fin. The advantages of a FinFET may include reducing the shortchannel effect and providing a higher current flow.

Although existing FinFET devices and methods of fabricating FinFETdevices have generally been adequate for their intended purposes, theyhave not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1I show perspective representations of various stages offorming a FinFET device structure, in accordance with some embodimentsof the disclosure.

FIGS. 2A-2I show cross-sectional representations of various stages offorming the FinFET device structure shown in FIGS. 1A-1I.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Some variations of the embodiments are described. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements. It should be understood that additionaloperations can be provided before, during, and after the method, andsome of the operations described can be replaced or eliminated for otherembodiments of the method.

The fins may be patterned by any suitable method. For example, the finsmay be patterned using one or more photolithography processes, includingdouble-patterning or multi-patterning processes. Generally,double-patterning or multi-patterning processes combine photolithographyand self-aligned processes, allowing patterns to be created that have,for example, pitches smaller than what is otherwise obtainable using asingle, direct photolithography process. For example, in one embodiment,a sacrificial layer is formed over a substrate and patterned using aphotolithography process. Spacers are formed alongside the patternedsacrificial layer using a self-alignment process. The sacrificial layeris then removed, and the remaining spacers may then be used to patternthe fins.

Embodiments for forming a fin field effect transistor (FinFET) devicestructure are provided. FIGS. 1A-1I show perspective representations ofvarious stages of forming a FinFET device structure 100, in accordancewith some embodiments of the disclosure.

Referring to FIG. 1A, a substrate 102 is provided. The substrate 102includes a first region 11 and a second region 12. The substrate 102 maybe made of silicon or other semiconductor materials. In someembodiments, the substrate 102 is a silicon wafer. Alternatively oradditionally, the substrate 102 may include other elementarysemiconductor materials such as germanium. In some embodiments, thesubstrate 102 is made of a compound semiconductor such as siliconcarbide, gallium arsenic, indium arsenide, or indium phosphide. In someembodiments, the substrate 102 is made of an alloy semiconductor such assilicon germanium, silicon germanium carbide, gallium arsenic phosphide,or gallium indium phosphide. In some embodiments, the substrate 102includes an epitaxial layer. For example, the substrate 102 has anepitaxial layer overlying a bulk semiconductor.

A material layer 103 is formed over the substrate 102. The materiallayer 103 and the substrate 102 are made of different materials. In someembodiments, the material layer 103 is made of silicon germanium (SiGe).The material layer 103 is formed by an epitaxial process. The epitaxialprocess may include a selective epitaxy growth (SEG) process, CVDdeposition techniques (e.g., vapor-phase epitaxy (VPE) and/or ultra-highvacuum CVD (UHV-CVD)), molecular beam epitaxy, or other suitable epiprocesses.

Afterwards, a dielectric layer 104 and a mask layer 106 are formed overthe substrate 102, and a photoresist layer 108 is formed over the masklayer 106. The photoresist layer 108 is patterned by a patterningprocess. The patterning process includes a photolithography process andan etching process. The photolithography process includes photoresistcoating (e.g., spin-on coating), soft baking, mask aligning, exposure,post-exposure baking, developing the photoresist, rinsing and drying(e.g., hard baking). The etching process may include a dry etchingprocess or a wet etching process.

The dielectric layer 104 is a buffer layer between the substrate 102 andthe mask layer 106. In addition, the dielectric layer 104 is used as astop layer when the mask layer 106 is removed. The dielectric layer 104may be made of silicon oxide. The mask layer 106 may be made of siliconoxide, silicon nitride, silicon oxynitride, or another applicablematerial. In some other embodiments, more than one mask layer 106 isformed over the dielectric layer 104.

The dielectric layer 104 and the mask layer 106 are formed by depositionprocesses, such as a chemical vapor deposition (CVD) process, ahigh-density plasma chemical vapor deposition (HDPCVD) process, aspin-on process, a sputtering process, or another applicable process.

Afterwards, as shown in FIG. 1B, after the photoresist layer 108 ispatterned, the dielectric layer 104 and the mask layer 106 are patternedby using the patterned photoresist layer 108 as a mask, in accordancewith some embodiments. As a result, a patterned dielectric layer 104 anda patterned mask layer 106 are obtained. Afterwards, the patternedphotoresist layer 108 is removed.

Afterwards, an etching process is performed on the material layer 103and the substrate 102 to form a number of fin structures 110 a, 110 b,110 c and 110 d by using the patterned dielectric layer 104 and thepatterned mask layer 106 as a mask. The first fin structure 110 a andthe second fin structure 110 b are formed in the first region 11. Thethird fin structure 110 c and the fourth fin structure 110 d are formedin the second region 12. A first pitch P₁ is between a sidewall surfaceof the first fin structure 110 a and a sidewall surface of the secondfin structure 110 b. A second pitch P₂ is between a sidewall surface ofthe third fin structure 110 c and a sidewall surface of the fourth finstructure 110 d. In some embodiments, the second pitch P₂ is greaterthan the first pitch P₁. In some embodiments, the first pitch P₁ is in arange from about 10 nm to about 40 nm. In some embodiments, the secondpitch P2 is in a range from about 20 nm to about 50 nm.

Each of the fin structures 110 a, 110 b, 110 c and 110 d has a topportion and a bottom portion. In some embodiments, the top portion ofeach of fin structures 110 a, 110 b, 110 c and 110 d is made of silicongermanium (SiGe), and the bottom portion is made of silicon (Si). Thesilicon germanium (SiGe) below a gate structure is used as a channelregion. The silicon germanium (SiGe) having compressive stress issuitable for providing increased carrier speed, i.e., increased holecarrier speed, for the channel region of P-type FinFET (PMOS device).

In some embodiments, each of the fin structures 110 a, 110 b, 110 c and110 d has a width that gradually increases from the top portion to thebottom portion. In other words, each of the fin structures 110 a, 110 bhas a tapered fin width which is gradually tapered from the bottomportion to the top portion.

The etching process may be a dry etching process or a wet etchingprocess. In some embodiments, the substrate 102 is etched using a dryetching process. The dry etching process includes using a fluorine-basedetchant gas, such as SF₆, C_(x)F_(y), NF₃ or a combination thereof. Theetching process may be a time-controlled process, and continue until thefin structures 110 a, 110 b reach a predetermined height.

As shown in FIG. 1C, after the fin structures 110 a, 110 b, 110 c and110 d are formed, a liner layer 112 is formed on the fin structures 110a, 110 b, 110 c and 110 d. More specifically, the liner layer 112 isconformally formed on the sidewall surfaces, top surface of the finstructures 110 a, 110 b, 110 c and 110 d, and on the mask layer 106.

The liner layer 112 is used to protect the fin structures 110 a, 110 b,110 c and 110 d from being damaged by the following processes (such asan anneal process or an etching process). Therefore, the profiles orshapes of the fin structures 110 a, 110 b, 110 c and 110 d aremaintained or preserved by the protection of the liner layer 112.

In some embodiments, the liner layer 112 is made of silicon nitride(SixNy). In some embodiments, the liner layer 112 is not made of oxide,such as silicon oxide. If the liner layer 112 made of silicon oxide, theliner layer 112 is not robust enough to protect the fin structures 110a, 110 b, 110 c and 110 d, especially when the fin structures 110 a, 110b, 110 c and 110 d include silicon germanium (SiGe). When the materiallayer 103 is made of silicon germanium (SiGe), silicon germanium (SiGe)is easily oxidized to form germanium oxide (GeOx) during the subsequentannealing process. Once the germanium oxide (GeOx) is formed, it iseasily removed by the etching process. Therefore, the profiles or shapeof the fin structures 110 a, 110 b, 110 c and 110 d will be changed. Inaddition, the germanium (Ge) concentration will be reduced due to theoxidation reaction.

Afterwards, as shown in FIG. 1D, an isolation layer 114 is formed tocover the fin structures 110 a, 110 b, 110 c and 110 d over thesubstrate 102, in accordance with some embodiments.

In some embodiments, the isolation layer 114 is made of silicon oxide,silicon nitride, silicon oxynitride, fluoride-doped silicate glass(FSG), or another low-k dielectric material. The isolation layer 114 maybe deposited by a deposition process, such as a chemical vapordeposition (CVD) process, a spin-on-glass process, or another applicableprocess.

In some embodiments, the isolation layer 114 is formed by a flowablechemical vapor deposition (FCVD) process. The isolation layer 114 issolidified by a UV curing process. Afterwards, an annealing process isperformed on the isolation layer 114 to improve the quality of theisolation layer 114. In some embodiments, the annealing process isperformed at a temperature in a range from about 400 degrees to about700 degrees. The patterned mask layer 106 and the liner layer 112 bothare used to protect the material layer 103 from being damaged during theannealing process, and therefore the profiles of the top portion of thefin structures 110 a, 110 b, 110 c and 110 d are not damaged by the hightemperature.

Next, as shown in FIG. 1E, the isolation layer 114 is thinned orplanarized to expose the top surface of the patterned mask layer 106, inaccordance with some embodiments. In some embodiments, the isolationlayer 114 is thinned by a chemical mechanical polishing (CMP) process.

Afterwards, as shown in FIG. 1F, a portion of the isolation layer 114 isremoved, in accordance with some embodiments. As a result, a top surfaceof the patterned mask layer 106 is exposed, and a portion of the linerlayer 112 is exposed.

Next, as shown in FIG. 1G, the patterned mask layer 106 is removed, inaccordance with some embodiments. In some embodiments, the patternedmask layer 106 is removed by a wet etching process. In some embodiments,the wet etching process includes using a phosphoric acid (H₃PO₄) etchingsolution.

Afterwards, as shown in FIG. 1H, an etching process 15 is performed onthe patterned dielectric layer 104, the liner layer 112 and theisolation layer 114, in accordance with some embodiments. The etchingprocess 15 is used to remove a portion of the liner layer 112 and aportion of the isolation layer 114. As a result, a first liner layer 112a, a second liner layer 112 b, a third liner layer 112 c, a fourth linerlayer 112 d and a fifth liner layer 112 e are obtained. In addition, afirst isolation structure 114 a, a second isolation structure 114 b, athird isolation structure 114 c, a fourth isolation structure 114 d anda fifth isolation structure 114 e are obtained.

The first fin structure 110 a has the inner sidewall surface and theouter sidewall surface. The inner sidewall surface of the first finstructure 110 a is close to the second fin structure 110 b and the outersidewall surface away from the second fin structure 110 b. The firstliner layer 112 a is formed on the outer sidewall surface of the firstfin structure 110 a, and the second liner layer 112 b is formed on theinner sidewall surface of the first fin structure 110 a. Note that thetop surface of the second liner layer 112 b is higher than the topsurface of the first liner layer 112 a. In some embodiments, the heightdifference between the top surface of the second liner layer 112 b andthe top surface of the first liner layer 112 a is in a range from about0.1 nm to about 2 nm.

The second liner layer 112 b is extended from the inner sidewall surfaceof the first fin structure 110 a to the inner sidewall surface of thesecond fin structure 110 b. The third liner layer 112 c is formed onouter sidewall surface of the second fin structure 110 b. Note that thetop surface of the second liner layer 112 b is higher than the topsurface of the third liner layer 112 c.

In addition, the third liner layer 112 c is extended from the outersidewall surface of the second fin structure 110 b to the outer sidewallsurface of the third fin structure 110 c. The fourth liner layer 112 dis formed on the inner sidewall surface of the third fin structure 110 cand on the inner sidewall surface of the fourth fin structure 110 d. Thefifth liner layer 112 e is formed on outer sidewall surface of thefourth fin structure 110 d. Note that the top surface of the fourthliner structure 112 d is higher than the top surface of the third linerlayer 112 c and the top surface of the fifth liner layer 112 e.Furthermore, the top surface of the fourth liner layer 112 d is lowerthan the top surface of the second liner layer 112 b. In other words,the top surface of the second liner layer 112 b is higher than the topsurface of the fourth liner layer 112 d.

The interface between the top portion and the bottom portion of thefirst fin structure 110 a is higher than the top surface of the firstliner layer 112 a and the top surface of the second liner layer 112 b.Similarly, the interface between the top portion and the bottom portionof the second fin structure 110 b is higher than the top surface of thesecond liner layer 112 b and the top surface of the third liner layer112 c. The interface between the top portion and the bottom portion ofthe third fin structure 110 c is higher than the top surface of thefourth liner layer 112 d. The interface between the top portion and thebottom portion of the fourth fin structure 110 d is higher than the topsurface of the fifth liner layer 112 e.

From the above descriptions, a portion of the liner layers which areformed on the inner sidewall surfaces of the fin structures are higherthan another portion of the liner layers which are formed on the outersidewall surfaces of the fin structures. When the distance of the twoadjacent fin structures is decreased, the height of the liner layerswhich are on the inner sidewall surfaces of the fin structures isincreased. For example, the first pitch P₁ between the first finstructure 110 a and the second fin structure 110 b is smaller than thesecond pitch P₂ between the third fin structure 110 c and the fourth finstructure 110 d. The second liner layer 112 b between the first finstructure 110 a and the second fin structure 110 b is higher than thefourth liner layer 112 d between the third fin structure 110 c and thefourth fin structure 110 d.

It should be noted that if the heights of inner liner layers are equalto or smaller than that of the outer liner layers, the fin structureswill be bent due to the uneven stress. In order to avoid fin bending,the heights of the inner liner layers are controlled to be higher thanthat of the outer liner layers.

The height difference between the inner liner layers and the outer linerlayers are controlled by using an etching process. In some embodiments,the etching process 15 includes a dry etching process. The dry etchingprocess includes multiple etching steps (or operations). In someembodiments, the etching gases include hydrogen fluoride (HF) gas,ammonia (NH₃) gas, and dilute gas (such as N₂ or Ar). The etching rateof the liner layer 112 and the etching rate of the isolation layer 114are controlled by adjusting the ratio of the flow rate of the etchinggas. In some embodiments, the ratio of the flow rate of HF to the flowrate of NH₃ is in a range from about 1:2 to about 1:20. If the ratio isnot within the above range, the inner liner layer will not be higherthan the outer liner layer. As a result, the bending problem of the finstructures 110 a, 110 b, 110 c and 110 d may be serious and theperformance of the FinFET device structure may be degraded.

As shown in FIG. 1H, a first spacing S₁ is between the top portion ofthe first fin structure 110 a and the top portion of the second finstructure 110 b. A second spacing S2 is between the interface of thefirst fin structure 110 a and the interface of the second fin structure110 b. Since the bending problems of the first fin structure 110 a andthe second fin structure 110 b are resolved by using inner liner layerhigher than the outer liner layer, the first spacing S₁ is substantiallyequal to the second spacing S₂.

The liner layer 112 and the isolation layer 114 are simultaneouslyremoved by the etching process 15. During the etching process 15, theisolation layer 114 (e.g. oxide layer) are mainly removed by the ammonia(NH₃) gas, and the liner layer 112 (e.g. silicon nitride) are mainlyremoved by the hydrogen fluoride (HF) gas. In order to decrease theamount of the liner layer 112 that is removed between the first finstructure 110 a and the second fin structure 110 b, the flow rate ofammonia (NH₃) gas is controlled to be higher than that of hydrogenfluoride (HF) gas. More specifically, when the pitch between the twoadjacent fin structures is decreased, the area ratio of the second linerlayer 112 b with respect to the second isolation structure 114 b isrelatively higher than that of first liner layer 112 a with respect tothe first isolation structure 114 a. That is, the area ratio of theinner liner layer with respect to the inner isolation layer is higherthan the area ratio of the outer liner layer with respect to the outerisolation layer. By increasing the flow rate of ammonia (NH₃) gas (ordecreasing the flow rate of hydrogen fluoride (HF) gas) in the etchingprocess 15, the amount of the inner liner layer that is removed is lessthan that of the outer liner layer. As a result, the top surface of theinner liner layer is higher than the top surface of the outer linerlayer.

For example, by increasing the flow rate of ammonia (NH₃) gas (ordecreasing the flow rate of hydrogen fluoride (HF) gas) in the etchingprocess 15, the amount of the second liner layer 112 b that is removedis less than that of the first liner layer 112 a. Therefore, the heightof the second liner layer 112 b is greater than the height of the firstliner layer 112 a. In other words, the top surface of the first linerstructure 112 a is lower than the top surface of the second liner layer112 b.

In some embodiments, the etching process 15 is operated at a pressure ina range from about 1 torr to about 5 torr. In some embodiments, theetching process 15 is operated at a temperature in a range from about100 degrees to about 150 degrees. When the pressure and the temperatureof the etching process 15 are kept within the range mentioned above, theetching efficiency of the etching process is improved. Furthermore, whenthe temperature of the etching process 15 is kept within the rangementioned above, the fin structure 110 is not oxidized or damaged.

Furthermore, in the region between the first fin structure 110 a and thesecond fin structure 110 b, the top surface of the second isolationstructure 114 b is lower than the top surface of the second liner layer112 a because the second isolation structure 114 b is mainly removed bylarge amount of ammonia (NH₃) gas. More specifically, the top surface ofthe first liner layer 112 a is higher than the top surface of the firstisolation structure 114 a, and the top surface of the second liner layer112 b is higher than the top surface of the second isolation structure114 b. Similarly, the top surface of the third liner layer 112 c ishigher than the top surface of the third isolation structure 114 c. Thetop surface of the fourth liner layer 112 d is higher than the topsurface of the fourth isolation structure 114 d.

As shown in FIG. 1H, each of the isolation structures 114 a, 114 b, 114c, 114 d and 114 e has a concave top surface. In the first region 11,the lowest point of the concave top surface of the second isolationstructure 114 b is higher than the lowest point of the concave topsurface of the first isolation structure 114 a. In the second region 12,a lowest point of the concave top surface of the fourth isolationstructure 114 d is higher than a lowest point of the concave top surfaceof the third isolation structure 114 c. Furthermore, the lowest point ofthe concave top surface of the second isolation structure 114 b ishigher than the lowest point of the concave top surface of the fourthisolation structure 114 d.

It should be noted that the etching gas in the etching process 15 is notexcited in a plasma state. In other words, in the etching process 15,plasma is not turned on. If the etching gas is operated at the plasmastate, the fin structures 110 a, 110 b, 110 c and 110 d may be damaged.Therefore, the profile and shape of the fin structures 110 a, 110 b, 110c and 110 d may be destroyed.

Furthermore, the etching process 15 includes a number of etching stepsand a cleaning step is between two etching steps. In some embodiments, afirst etching step is performed for a period of time in a range fromabout 1 second to about 30 seconds, a cleaning step is performed afterthe first etching step for a period of time in a range from about 60second to about 300 seconds, and a second etching step is performedafter the cleaning step. Note that during the cleaning step, the etchinggas is stopped. The cleaning step is used to remove the unwantedresidues and byproducts generated from the etching steps. The etchingefficiency of the etching process 15 is improved. The cleaning step isperformed in-situ without transferred to another chamber. Therefore,pollution is avoided and throughput is improved.

Next, as shown in FIG. 1I, a gate dielectric layer 116 is formed on thefin structures 110 a, 110 b, 110 c and 110 d, the isolation structures114 a, 114 b, 114 c, 114 d and 114 e and a gate electrode layer 118 isformed on the gate dielectric layer 116, in accordance with someembodiments. A gate structure 120 is constructed by the gate dielectriclayer 116 and the gate electrode layer 118. In some embodiments, thegate dielectric layer 116 is a dummy gate dielectric layer and the gateelectrode layer 118 is a dummy gate electrode layer. The dummy gatedielectric layer and the dummy gate electrode layer may be replaced bythe following steps to form a real gate structure with a high-kdielectric layer and a metal gate electrode layer.

The gate dielectric layer 116 includes a first portion and a secondportion, the first portion is directly over the first liner layer 112 aand the second portion is directly over the second liner layer 112 b.Due to the height difference between the first liner layer 112 a and thesecond liner layer 112 b, the bottom surface of the second portion ofthe gate dielectric layer 116 is higher than the bottom surface of thefirst portion of the gate dielectric layer 116.

In some embodiments, the gate dielectric layer 116 may includedielectric materials, such as silicon oxide, silicon nitride, siliconoxynitride, dielectric material(s) with high dielectric constant(high-k), or combinations thereof. In some embodiments, the gateelectrode layer 118 is made of polysilicon. The gate dielectric layer116 and the gate electrode layer 118 are independently formed by adeposition process, such as chemical vapor deposition (CVD), physicalvapor deposition (PVD), atomic layer deposition (ALD), high densityplasma CVD (HDPCVD), metal organic CVD (MOCVD), or plasma enhanced CVD(PECVD).

Afterwards, a pair of spacer layers (not shown) are formed on oppositesidewalls of the gate structure 120, in accordance with someembodiments. More specifically, the spacer layers 120 are formed onsidewall surfaces of the gate electrode layer 118. The spacer layers maybe made of silicon oxide, silicon nitride, silicon oxynitride, and/ordielectric materials. In some embodiments, the spacer layers are formedby a chemical vapor deposition (CVD) process, a spin-on-glass process,or another applicable process.

Afterwards, a top portion of the fin structures 110 a, 110 b, 110 c, and110 d is removed to form a recess (not shown), and the source/drain(S/D) structures (not shown) are formed in the recess. The source/drain(S/D) structures are formed on opposite sidewall surfaces of the gatestructure 120.

Afterwards, an inter-layer dielectric (ILD) material is formed over thefin structures 110 a, 110 b, 110 c and 110 d, and over the gatestructure 120. Next, the ILD material is planarized to form the ILDstructure.

Next, the dummy gate dielectric layer 116 and the dummy gate electrodelayer 118 are removed to form a trench, and the real gate dielectriclayer and metal gate electrode layer (not shown) are filled into thetrench. In some embodiments, a work function layer (not shown) may beformed between the gate dielectric layer and the gate electrode layer.Afterwards, the FinFET device structure 100 continues to form otherdevices or structures.

FIGS. 2A-2I show cross-sectional representations of various stages offorming the FinFET device structure 100 shown in FIGS. 1A-1I. FIGS.2A-2I show cross-sectional representations taken along line aa′ in FIGS.1A-1I. Some processes and materials used to form the FinFET devicestructure in FIGS. 1A-1I are similar to, or the same as, those used toform the FinFET structure 100 in FIGS. 2A-2I and are not repeatedherein.

As shown in FIG. 2A, the substrate 102 includes the first region 11 andthe second region 12. The material layer 103 is formed over thesubstrate 102, and the dielectric layer 104 and the mask layer 106 aresequentially formed on the material layer 103. Afterwards, thephotoresist layer 108 is formed over the mask layer 106 and it ispatterned to form a patterned photoresist layer 108.

Next, as shown in FIG. 2B, the dielectric layer 104 and the mask layer106 are patterned by using the patterned photoresist layer 108 as amask, in accordance with some embodiments. Afterwards, the materiallayer 103 and the substrate 102 are patterned to form a number of finstructures 110 a, 110 b, 110 c and 110 d. In the first region 11, thefirst pitch P₁ is between a sidewall surface of the first fin structure110 a and a sidewall surface of the second fin structure 110 b. Thesecond pitch P₂ is between a sidewall surface of the third fin structure110 c and a sidewall surface of the fourth fin structure 110 d. In someembodiments, the second pitch P₂ is greater than the first pitch P₁.

Afterwards, as shown in FIG. 2C, the liner layer 112 is formed on thefin structures 110 a, 110 b, 110 c and 110 d. More specifically, theliner layer 112 is conformally formed on the sidewall surfaces and thetop surface of the fin structures 110 a, 110 b, 110 c and 110 d, and onthe mask layer 106, in accordance with some embodiments. The liner layer112 is used to protect the fin structures 110 a, 110 b, 110 c and 110 dfrom being damaged by the following processes (such as an anneal processor an etching process). In some embodiments, the liner layer 112 is madeof silicon nitride (SixNy).

Next, as shown in FIG. 2D, the isolation layer 114 is formed to coverthe fin structures 110 a, 110 b, 110 c and 110 d over the substrate 102,in accordance with some embodiments.

Afterwards, as shown in FIG. 2E, the isolation layer 114 is thinned orplanarized to expose the top surface of the patterned mask layer 106, inaccordance with some embodiments. In some embodiments, the isolationlayer 114 is thinned by a chemical mechanical polishing (CMP) process.

Afterwards, as shown in FIG. 2F, a portion of the isolation layer 114 isremoved, in accordance with some embodiments. As a result, a top surfaceof the patterned mask layer 106 is exposed, and a portion of the linerlayer 112 is exposed.

Next, as shown in FIG. 2G, the patterned mask layer 106 is removed, inaccordance with some embodiments. In some embodiments, the patternedmask layer 106 is removed by a wet etching process.

Afterwards, as shown in FIG. 2H, an etching process 15 is performed onthe patterned dielectric layer 104 and the liner layer 112, inaccordance with some embodiments. The etching process 15 is used toremove the patterned dielectric layer 104, a portion of the liner layer112 and a portion of the isolation layer 114. As a result, the firstliner layer 112 a, the second liner layer 112 b, the third liner layer112 c, the fourth liner layer 112 d and the fifth liner layer 112 e areobtained. In addition, the first isolation structure 114 a, the secondisolation structure 114 b, the third isolation structure 114 c, thefourth isolation structure 114 d and the fifth isolation structure 114 eare obtained.

In the first region 11, the first fin structure 110 a has the innersidewall surface and the outer sidewall surface, the inner sidewallsurface is close to the second fin structure 110 b and the outersidewall surface is far away from the second fin structure 110 b. Theouter fin height of the first fin structure 110 a is defined as H₁ whichis measured from a top surface of the first liner layer 112 a to a topsurface of the first fin structure 110 a. The inner fin height of thefirst fin structure 110 a is defined as H2 which is measured from a topsurface of the second liner layer 112 b to the top surface of the firstfin structure 110 a. The inner fin height H₂ is smaller than the outerfin height H₁. In some embodiments, the height difference (ΔH=H₁−H₂)between the top surface of the first liner layer 112 a and the topsurface of the second liner layer 112 b is in a range from about 0.1 nmto about 2 nm. In some embodiments, the outer fin height H₁ of the firstfin structure 110 a is in a range from about 45 nm to about 60 nm. Insome embodiments, the inner fin height H₂ of the first fin structure 110a is in a range from about 43 nm to about 58 nm.

In the second region 12, the third fin structure 110 c has the innersidewall surface and the outer sidewall surface, the inner sidewallsurface is close to the fourth fin structure 110 d and the outersidewall surface is far away from the fourth fin structure 110 d. Theouter fin height of the third fin structure 110 c is defined as H₃ whichis measured from a top surface of the third liner layer 112 c to a topsurface of the third fin structure 110 c. The inner fin height of thethird fin structure 110 c is defined as H₄ which is measured from a topsurface of the fourth liner layer 112 d to the top surface of the thirdfin structure 110 c. The inner fin height H₄ is smaller than the outerfin height H₃. In addition, the inner fin height H₂ of the first finstructure 110 a is smaller than the inner fin height H₄ of the third finstructure 110 c. In some embodiments, the height difference (ΔH=H₃−H₄)between the top surface of the third liner layer 112 c and the topsurface of the fourth liner layer 112 d is in a range from about 0.1 nmto about 2 nm. In some embodiments, the outer fin height H₃ of the thirdfin structure 110 c is in a range from about 47 nm to about 62 nm. Insome embodiments, the inner fin height H₄ of the third fin structure 110c is in a range from about 45 nm to about 60 nm.

As shown in FIG. 2H, the top surface of the second isolation structure114 b is higher than the top surface of the first isolation structure114 a. In addition, the top surface of the second isolation structure114 b is higher than the top surface of the fourth isolation structure114 d.

Due to the protection of the higher inner second liner layer 112 b, thefirst fin structure 110 a and the second fin structure 110 b are notbent after the etching process 15. Similarly, the third fin structure110 c and the fourth fin structure 110 d are not bent after the etchingprocess 15 due to the higher inner fourth liner layer 112 d.

Next, as shown in FIG. 2I, the gate dielectric layer 116 is formed onthe fin structures 110 a, 110 b, 110 c and 110 d, the isolationstructures 114 a, 114 b, 114 c, 114 d and 114 e and the gate electrodelayer 118 is formed on the gate dielectric layer 116, in accordance withsome embodiments. Afterwards, the FinFET device structure 100 continuesto form other devices or structures.

It should be noted that fin bending problem is prevented due toformation of the inner liner layer higher than the outer liner layer.The fin profile and fin shape are maintained because the liner layer 112is formed on the sidewall surfaces of the fin structures 110 a, 110 b,110 c and 110 d. The heights of the liner layers 112 a, 112 b, 112 c,112 d and 112 e are controlled by using the etching process 15 withdifferent etching rate for removing the liner layer 112 and theisolation layer 114.

Embodiments for forming a FinFET device structure and method forformation of the same are provided. The FinFET device structure includesa first fin structure and a second fin structure extending above asubstrate. The first liner layer is formed on an outer sidewall surfaceof the first fin structure, and the second liner layer is formed on aninner sidewall surface of the first fin structure. A top surface of thesecond liner layer is higher than a top surface of the first linerlayer. The inner liner layer is higher than the outer liner layer toprevent the fin bending problems. Therefore, the performance of theFinFET device structures is improved.

In some embodiments, a fin field effect transistor (FinFET) devicestructure is provided. The FinFET device structure includes a first finstructure extending above a substrate, and the first fin structureincludes a bottom portion and a top portion, and the top portion is madeof silicon germanium (SiGe). The FinFET device structure includes asecond fin structure adjacent to the first fin structure, and the firstfin structure includes an inner sidewall surface close to the second finstructure and an outer sidewall surface away from the second finstructure. The FinFET device structure also includes a first liner layerformed on the outer sidewall surface of the first fin structure and asecond liner layer formed on the inner sidewall surface of the first finstructure. The FinFET device structure further includes a firstisolation structure formed on the substrate, and the first liner layeris between the first isolation structure and the first fin structure,and a top surface of the second liner layer is higher than a top surfaceof the first liner layer.

In some embodiments, a FinFET device structure is provided. The FinFETdevice structure includes a substrate, and the substrate includes afirst region and a second region. The FinFET device structure includes afirst fin structure and a second fin structure extending above the firstregion of the substrate, and the first fin structure includes a bottomportion and a top portion, the top portion is made of silicon germanium(SiGe), a first pitch between the first fin structure and the second finstructure. The FinFET device structure further includes a third finstructure and a fourth fin structure extending above the second regionof the substrate. The third fin structure is between the second finstructure and the fourth fin structure, and a second pitch is betweenthe third fin structure and the fourth fin structure, and the secondpitch is greater than the first pitch. The FinFET device structure alsoincludes a first liner layer formed on an inner sidewall surface of thefirst fin structure and an inner sidewall surface of the second finstructure and a second liner layer formed on an outer sidewall surfaceof the second fin structure and an outer sidewall surface of the thirdfin structure. A top surface of the first liner layer is higher than atop surface of the second liner layer.

In some embodiments, a method for forming a FinFET device structure isprovided. The method includes forming a first fin structure and a secondfin structure over a substrate and forming a liner layer over the firstfin structure and the second fin structure. The method also includesforming an isolation layer over the liner layer and removing a portionof the liner layer and a portion of the isolation layer, such that theliner layer includes a first liner layer on an outer sidewall surface ofthe first fin structure and a second liner layer on an inner sidewallsurface of the first fin structure, and a top surface of the secondliner layer is higher than a top surface of the first liner layer.

In some embodiments, a method for forming a FinFET device structure isprovided. The method include forming a first fin structure and a secondfin structure over a substrate, and the first fin structure has a firstbottom portion and a first top portion, and a first interface is betweenthe first bottom portion and the first top portion, and the second finstructure has a second bottom portion and a second top portion, and asecond interface is between the second bottom portion and the second topportion. The method also includes forming a liner layer over the firstfin structure and the second fin structure, and forming an isolationlayer over the liner layer. The method further includes removing a firstportion of the isolation layer to expose a portion of the liner layer.The method includes removing a first portion of the liner layer, suchthat a top surface of the liner layer is lower than a top surface of theisolation layer. The method includes simultaneously removing a secondportion of the isolation layer and a second portion of the liner layerto form an isolation structure between the first fin structure and thesecond fin structure, wherein the liner layer comprises a first linerlayer on an inner sidewall of the first fin structure and a second linerlayer on an outer sidewall of the second fin structure. The first linerlayer is in direct contact with the first interface, and the secondliner layer is lower than a top surface of the second interface.

In some embodiments, a method for forming a FinFET device structure isprovided. The method includes forming a first fin structure and a secondfin structure over a first region of a substrate, wherein the first finstructure has a first bottom portion and a first top portion, and afirst interface is between the first bottom portion and the first topportion. The method also includes forming a third fin structure and afourth fin structure over a second region of the substrate, wherein thethird fin structure has a third bottom portion and a third top portion,and a third interface is between the third bottom portion and the thirdtop portion. The method includes forming a liner layer over the firstfin structure, the second fin structure, the third fin structure and thefourth fin structure. The method includes forming an isolation layerover the liner layer, and removing a portion of the isolation layer anda portion of the liner layer to form a first isolation structure betweenthe first fin structure and the second fin structure, a second isolationstructure between the second fin structure and the third fin structure.A bottommost point of the first isolation structure is higher than abottommost point of the second isolation structure and lower than thefirst interface.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a fin field effecttransistor (FinFET) device structure, comprising: forming a first finstructure and a second fin structure over a substrate, wherein the firstfin structure comprises a first sidewall and a second sidewalloppositely to the first sidewall; forming a liner layer over the firstfin structure and the second fin structure; forming an isolation layerover the liner layer; and removing a portion of the liner layer and aportion of the isolation layer, such that the liner layer comprises afirst liner layer on the first sidewall surface of the first finstructure and a second liner layer on the second sidewall surface of thefirst fin structure, and a top surface of the second liner layer ishigher than a top surface of the first liner layer.
 2. The method forforming the fin field effect transistor (FinFET) device structure asclaimed in claim 1, wherein removing the portion of the liner layer andthe portion of the isolation layer comprises performing a dry etchingprocess with an etching gas, and the etching gas is not excited in aplasma state.
 3. The method for forming the fin field effect transistor(FinFET) device structure as claimed in claim 2, wherein the dry etchingprocess comprises a first etching step, a cleaning step and a secondetching step, the cleaning step is performed before the second etchingstep, and the etching gas is stopped during the cleaning step.
 4. Themethod for forming the fin field effect transistor (FinFET) devicestructure as claimed in claim 1, further comprising: forming adielectric layer on the first fin structure and the second finstructure; forming a hard mask layer on the dielectric layer; formingthe liner layer over the hard mask layer; removing a portion of theisolation layer, such that a top surface of the isolation layer ishigher than a top surface of the hard mask layer; removing the hard masklayer; and simultaneously removing the dielectric layer, the portion ofthe liner layer and the portion of the isolation layer.
 5. The methodfor forming the fin field effect transistor (FinFET) device structure asclaimed in claim 1, wherein the first fin structure has a first bottomportion and a first top portion, the first bottom portion and the firsttop portion of the first fin structure are made of different materials,and an interface between the first top portion and the first bottomportion is in direct contact with the second liner layer.
 6. The methodfor forming the fin field effect transistor (FinFET) device structure asclaimed in claim 5, further comprising: forming an isolation structureafter removing the portion of the liner layer and the portion of theisolation layer, wherein the interface is higher than a top surface ofthe isolation structure.
 7. The method for forming the fin field effecttransistor (FinFET) device structure as claimed in claim 5, wherein theinterface is higher than a top surface of the first liner layer.
 8. Themethod for forming the fin field effect transistor (FinFET) devicestructure as claimed in claim 1, further comprising: forming a gatedielectric layer over the first fin structure, the second fin structure,the first liner layer and the second liner layer, wherein the gatedielectric layer comprise a first portion on the first liner layer and asecond portion on the second liner layer, a bottom surface of the firstportion of the gate dielectric layer is lower than a bottom surface ofthe second portion of the gate dielectric layer.
 9. The method forforming the fin field effect transistor (FinFET) device structure asclaimed in claim 1, wherein the second fin structure has a second bottomportion and a second top portion, the second bottom portion and thesecond top portion of the second fin structure are made of differentmaterials, and an interface between the second top portion and thesecond bottom portion is higher than the top surface of the first linerlayer.
 10. A method for forming a fin field effect transistor (FinFET)device structure, comprising: forming a first fin structure and a secondfin structure over a substrate, wherein the first fin structure has afirst bottom portion and a first top portion, and a first interface isbetween the first bottom portion and the first top portion, and thesecond fin structure has a second bottom portion and a second topportion, and a second interface is between the second bottom portion andthe second top portion; forming a liner layer over the first finstructure and the second fin structure; forming an isolation layer overthe liner layer; removing a first portion of the isolation layer toexpose a portion of the liner layer; removing a first portion of theliner layer, such that a top surface of the liner layer is lower than atop surface of the isolation layer; and simultaneously removing a secondportion of the isolation layer and a second portion of the liner layerto form an isolation structure between the first fin structure and thesecond fin structure, wherein the liner layer comprises a first linerlayer on an inner sidewall of the first fin structure and a second linerlayer on an outer sidewall of the second fin structure, the first linerlayer is in direct contact with the first interface, and the secondliner layer is lower than a top surface of the second interface.
 11. Themethod for forming the fin field effect transistor (FinFET) devicestructure as claimed in claim 10, further comprising: forming adielectric layer on the first fin structure and the second finstructure; forming a hard mask layer on the dielectric layer; andforming the liner layer on the hard mask layer, wherein a top surface ofthe hard mask layer is exposed while removing the first portion of theisolation layer to expose the portion of the liner layer.
 12. The methodfor forming the fin field effect transistor (FinFET) device structure asclaimed in claim 10, further comprising: removing the hard mask layer toexpose a top surface of the dielectric layer and to form a recess in theisolation layer while removing the first portion of the liner layer. 13.The method for forming the fin field effect transistor (FinFET) devicestructure as claimed in claim 10, wherein the isolation structurecomprises a first isolation structure in direct contact with the firstliner layer and a second isolation structure in direct contact with thesecond liner layer, the top surface of the first isolation structure isa concave top surface, and the top surface of the second isolationstructure is a concave top surface.
 14. The method for forming the finfield effect transistor (FinFET) device structure as claimed in claim13, wherein a topmost point of the first isolation structure is higherthan a topmost point of the second isolation structure.
 15. The methodfor forming the fin field effect transistor (FinFET) device structure asclaimed in claim 13, wherein a lowest point of the concave top surfaceof the first isolation structure is higher than a lowest point of theconcave top surface of the second isolation structure and lower than thefirst interface.
 16. A method for forming a fin field effect transistor(FinFET) device structure, comprising: forming a first fin structure anda second fin structure over a first region of a substrate, wherein thefirst fin structure has a first bottom portion and a first top portion,and a first interface is between the first bottom portion and the firsttop portion; forming a third fin structure and a fourth fin structureover a second region of the substrate, wherein the third fin structurehas a third bottom portion and a third top portion, and a thirdinterface is between the third bottom portion and the third top portion;forming a liner layer over the first fin structure, the second finstructure, the third fin structure and the fourth fin structure; formingan isolation layer over the liner layer; and removing a portion of theisolation layer and a portion of the liner layer to form a firstisolation structure between the first fin structure and the second finstructure, a second isolation structure between the second fin structureand the third fin structure, wherein a bottommost point of the firstisolation structure is higher than a bottommost point of the secondisolation structure and lower than the first interface.
 17. The methodfor forming the fin field effect transistor (FinFET) device structure asclaimed in claim 16, wherein a first pitch is between the first finstructure and the second fin structure, a second pitch is between thethird fin structure and the fourth fin structure, and the second pitchis greater than the first pitch.
 18. The method for forming the finfield effect transistor (FinFET) device structure as claimed in claim16, wherein the liner layer comprises a first liner layer between thefirst fin structure and the second fin structure and a second linerlayer between the second fin structure and the third fin structure, andthe first liner layer is in direct contact with the first interface. 19.The method for forming the fin field effect transistor (FinFET) devicestructure as claimed in claim 16, wherein the top surface of the firstisolation structure is a concave top surface, and the top surface of thesecond isolation structure is a concave top surface.
 20. The method forforming the fin field effect transistor (FinFET) device structure asclaimed in claim 16, further comprising: forming a gate dielectric layerover the first fin structure, the second fin structure, the third finstructure, fourth fin structure, the first isolation structure and thesecond isolation structure, wherein the gate dielectric layer comprisesa first portion on the first isolation structure and a second portion onthe second isolation structure, a bottom surface of the second portionof the gate dielectric layer is lower than a bottom surface of the firstportion of the gate dielectric layer.